Abstract: An element recovery method and an element recovery apparatus are provided by which an element containing a high-purity rare earth element can be recovered at low cost. The element recovery method includes the steps of: preparing molten salt containing a rare earth element; and controlling electric potentials in a pair of electrode members at prescribed values while keeping the pair of electrode members in contact with the molten salt, thereby depositing the rare earth element existing in the molten salt on one of the pair of electrode members. In this way, as compared with the conventional wet separation method, an element such as a rare earth element that is to be recovered can be directly recovered from the molten salt in which the element is dissolved, so that the steps of the recovery method can be simplified and reduced in cost.

Abstract: A molten salt battery is provided which includes a positive electrode including a positive-electrode active material represented by the general formula: An(1?x)M1nxFe1?yM2yP2O7 (wherein n is 1 or 2, 0?x?0.5, 0?y?0.5, A is an alkali metal element, M1 is an element other than the element A, M2 is an element other than Fe), a negative electrode including a negative-electrode active material, a separator interposed between the positive electrode and the negative electrode, and a molten salt electrolyte. The molten salt electrolyte contains 90% by mass or more of an ionic liquid containing a salt of the element A.

Abstract: A novel method for purifying hydrogen fluoride, capable of efficiently reducing the content of arsenic in hydrogen fluoride. The method includes the steps of (a) bringing a crude hydrogen fluoride containing arsenic trifluoride into contact with an oxidizing agent of a metal fluoride in a liquid state in a reactor to obtain a reaction mixture, wherein arsenic pentafluoride is formed by oxidizing arsenic trifluoride with the oxidizing agent of the metal fluoride through a liquid-liquid reaction; and (b) separating purified hydrogen fluoride from the reaction mixture by a separator, the thus obtained purified hydrogen fluoride having a lower content of arsenic than that of the crude hydrogen fluoride.

Abstract: As a molten salt composition lacking a clear melting point and including a molten salt that can be suitably used as an electrolytic solution of a secondary battery, there is provided a molten salt composition including a mixture of two or more kinds of molten salts which can be used as an electrolytic solution of a secondary battery. Particularly, provided is a molten salt composition comprising two kinds of molten salts each having cations with ion diameters different from each other, composition ratio being set to a composition ratio within a range in which the molten salt composition lacks a melting point. Also provided is a secondary battery including the molten salt composition as an electrolytic solution, which can maintains an available state even when the temperature becomes low without rapidly becoming unavailable.

Abstract: Provided is a method for operating a molten salt battery having a sodium compound (NaCrO2) in a positive electrode and tin (Sn) in a negative electrode with a molten salt as an electrolytic solution. Although the operating temperature range of the molten salt battery is originally from 57° C. to 190° C., the molten salt battery is operated with an internal temperature thereof (temperature of electrodes and molten salt) set at from 98° C. to 190° C. to cause sodium to turn to a liquid phase. The sodium penetrates into a Sn—Na alloy micronized in the negative electrode, so that separation of the Sn—Na alloy is suppressed.

Abstract: An element recovery method and an element recovery apparatus are provided by which an element containing a high-purity rare earth element can be recovered at low cost. The element recovery method includes the steps of: preparing molten salt containing a rare earth element; and controlling electric potentials in a pair of electrode members at prescribed values while keeping the pair of electrode members in contact with the molten salt, thereby depositing the rare earth element existing in the molten salt on one of the pair of electrode members. In this way, as compared with the conventional wet separation method, an element such as a rare earth element that is to be recovered can be directly recovered from the molten salt in which the element is dissolved, so that the steps of the recovery method can be simplified and reduced in cost.

Abstract: A separator (3) of a molten salt battery is impregnated with a molten salt that serves as the electrolyte. The molten salt contains, as cations, at least one kind of ions selected from among quaternary ammonium ions, imidazolium ions, imidazolinium ions, pyridinium ions, pyrrolidinium ions, piperidinium ions, morpholinium ions, phosphonium ions, piperazinium ions and sulfonium ions in addition to sodium ions. These cations do not have adverse effects on a positive electrode (1). In addition, the melting point of the molten salt, which contains sodium ions and the above-mentioned cations, is significantly lower than the operating temperature of sodium-sulfur batteries, said operating temperature being 280-360 DEG C. Consequently, the molten salt battery is capable of operating at lower temperatures than sodium-sulfur batteries.

Abstract: A molten salt composition is disclosed containing two or more types of molten salt MTFSI whose anion is an imide anion TFSI and whose cation is an alkali metal M exhibits a lower electrolyte melting point and a wider operating temperature range than a simple salt does. This brings about various advantages such as a wider range of materials that are chosen for use in batteries and the like.

Abstract: A battery including a positive electrode, a negative electrode mainly composed of sodium, and an electrolyte provided between the positive electrode and the negative electrode, the electrolyte being molten salt containing anions expressed with chemical formula (I) below and cations of metal, R1 and R2 in the chemical formula (I) above independently representing fluorine atom or fluoroalkyl group, the cations of metal containing at least one of at least one type of cations of alkali metal and at least one type of cations of alkaline-earth metal, as well as an energy system including the battery are provided.

Abstract: To provide a novel method for purifying hydrogen fluoride, capable of efficiently reducing the content of arsenic in hydrogen fluoride. The step (a) of bringing a crude hydrogen fluoride containing arsenic trifluoride into contact with an oxidizing agent of a metal fluoride in a liquid state is carried out, for example, in a reactor (11) to obtain a reaction mixture wherein arsenic pentafluoride is formed by oxidizing arsenic trifluoride with the oxidizing agent of the metal fluoride through a liquid-liquid reaction; and the step (b) of separating purified hydrogen fluoride from the reaction mixture is carried out, for example, by a separator (13), the thus obtained purified hydrogen fluoride having a lower content of arsenic than that of the crude hydrogen fluoride.

Abstract: A molten salt composition is disclosed containing two or more types of molten salt MTFSI whose anion is an imide anion TFSI and whose cation is an alkali metal M exhibits a lower electrolyte melting point and a wider operating temperature range than a simple salt does. This brings about various advantages such as a wider range of materials that are chosen for use in batteries and the like.

Abstract: An objective of the present invention is to provide an electrodeposition method for metals using a molten salt, which easily enables the electrodeposition of various types of metals such as refractory metals and rare earth metals. In order to solve this problem, the invention is characterized in that it is effected at the electrodeposition temperature in a range of from 100° C. to 200° C.

Abstract: There is disclosed a method for producing a graphite fluoride for use in an electrochemical cell of the type having as the negative electrode a light metal, such as an alkali metal, an electrolyte in which the negative electrode is not dissolved, and a positive electrode which has, as an active material, a graphite fluoride produced by fluorinating a decomposition residual carbon which has been obtained by decomposing a covalent intercalation compound. The electrochemical cell of the present invention exhibits high discharge potential and low overvoltage, and excellent discharge characteristics with respect to the flatness of discharge voltage, discharge capacity and shelf-life.